Reason for performing study: The aetiological factors behind impinged or overriding of dorsal spinous processes ('kissing spine syndrome', KSS) are not clearly understood. Back conformation, breed, age, training and gender may play important roles in this condition. Radiographic changes vary and abnormalities are seen in many clinically normal horses, but the conclusion of previous studies in mature horses is that interspinous spaces <4 mm are considered too narrow and potentially indicative of KSS. Objectives: To evaluate whether narrowing of the interspinous space was present in a population of normal Warmblood foals. Materials and methods: The mean interspinous space width in the area of T10-L1 was measured on radiographs from 25 Warmblood foals aged 9-88 days. Results: Mean +/- s.d. interspinous space width was found to be between 5.9 +/- 1.2 and 8.9 +/- 2.6 mm with the narrowest space in the area T16-T17 and the widest space in T10-T12. No interspinous spaces were <4 mm wide. Gender and location of the interspinous space significantly affected the width of the distance between the spinous processes. Conclusions and potential relevance: In this study none of the interspinous spaces were <4 mm and therefore none of the foals showed signs of impinged or overriding of dorsal spinous processes known as KSS based on the current definitions. Consequently, in this population, there did not appear to be a congenital narrowing of the interspinous space. However, long-term follow-up studies, including detailed information on imposed factors such as training, are needed in order to further elucidate a possible congenital component in the aetiology of KSS.